Geothermal power generation facilities generally generate power by excavating the underground to a specific depth so as to make geothermal fluid, which includes steam and hot water that coexist under high pressure at a deep underground part, erupt to the ground, separating the geothermal fluid into steam and hot water with a separator, and rotationally driving a turbine with the separated steam.
There is also known binary cycle power generation which uses heat media (inflammable media) lower in boiling point than water, such as ammonia, pentane and chlorofluorocarbon, as working fluid, so that even when underground temperature and/or pressure are low and only hot water is available, power generation can be performed by boiling the heat media with the hot water and thereby driving a turbine.
These geothermal power generation facilities are generally installed in mountainous regions which lack a water source. Under these circumstances, it is difficult to adopt a water cooling-type device for cooling the facilities, and therefore air cooling-type cooling towers and the like are adopted. Unfortunately, the air cooling-type device is larger in power consumption and less efficient in cooling the facilities than the water cooling-type device.
One of the solutions to these problems is disclosed, for example, in PTL 1.
PTL 1 discloses an emergency cooling device in an organic medium-applied power recovery plant, the plan including: a primary pipe for circulating a heat source fluid; and a closed-loop secondary pipe for circulating a low-boiling point organic medium as a working medium, the secondary pipe being equipped with an evaporator that evaporates the working medium through heat exchange with the heat source fluid in the primary pipe, a turbine driven with generated medium steam, a condenser that condenses exhaust steam of the turbine, and a bypass pipe that bypasses the turbine and communicates with the condenser from the evaporator side, the bypass pipe being opened at the time of emergency shutdown of the plant. The emergency cooling device supplies a cooling fluid to a portion of the primary pipe that is upstream of the evaporator at the time of emergency shutdown of the plant.
It is stated that since the cooling fluid is supplied to a portion of the primary pipe that is upstream of the evaporator at the time of emergency shutdown of the plant, it becomes possible to prevent continuous generation of the working medium in the evaporator after emergency shutdown and to thereby lower the temperature of the heat source fluid inside the evaporator to the level where pyrolysis of the working medium is negligible. It is stated that in this case, a heat source fluid that is reserved and cooled or a heat-exchanged heat source fluid returning from the downstream of the evaporator is used as the cooling fluid of the emergency cooling device, so that the heat source fluid can easily be secured.